Unless you set StorageCharacteristics property to scRemovableMedia, the disk is fixed. However you indeed don't get an entry in Disk Manager snap-in in MMC. This is because physical device is not emulated. This will be supported in version 2 of CallbackDisk, which is in development now. We already have this functionality in Callback File System, so now we are porting it to SolFS Driver Edition and to CallbackDisk.

If you need this functionality now, maybe you can make use of Callback File System. It's slightly different as it doesn't work with disk images, but with files. However, in some scenarios it would work as a replacement for CallbackDisk.